From KUNC (Luke Runyon):
The latest Bureau of Reclamation reservoir projections, which take into account river flows in a given year, show a likelihood that Lake Mead on the Arizona-Nevada stateline will dip below the critical threshold of 1,075 feet in elevation in May and remain below that level for the foreseeable future.
A first-ever official shortage declaration from the Department of the Interior is almost certain later this year. According to the terms of a 2007 agreement, a shortage is declared by the Interior Secretary after consulting with water users in the Lower Basin states of California, Arizona and Nevada. An August report is used to forecast when Lake Mead will be below 1,075 feet at the start of a calendar year.
Extreme to exceptional drought conditions have blanketed more than 75% of the river’s upper watershed for more than eight months. The majority of the river’s water comes from high mountain snowpack in Colorado and Wyoming. Both states are dealing with drought of varying degrees of severity.
“Current conditions resemble 2002, 2012, 2013 and the beginning of 2018, four out of the five driest years on record,” the Bureau of Reclamation report notes.
The Colorado River’s two biggest reservoirs, Lakes Mead and Powell, have been unable to recover from sustained hot and dry conditions for the last 21 years, a phenomenon scientists link to human-induced climate change. Warmer temperatures have increased the amount of evaporation from streams and reservoirs, raised demand for water in forests and on crop fields, and changed precipitation from snow to rain. Snow acts as a large, frozen reservoir that melts slowly over months, while rain is harder to capture and dole out to farmers, cities and other users.
Top water officials in Arizona and southern California say they are prepared for the coming cutbacks to their water supplies. If the dry conditions hold, Arizona, Nevada and Mexico could take increasingly steep cuts to what they’re allowed to divert from the river. California could also see its river allocation restricted if the declines continue.
The basin has flirted with a shortage declaration for the last decade but has been aided by short-term boosts in snowpack, coordinated releases of water between Lakes Powell and Mead, and voluntary conservation by Lower Basin water users. Arizona, Nevada and Mexico have already been curtailed due to restrictions laid out in the 2019 Drought Contingency Plan. A shortage declaration will make those cutbacks even steeper.
In response to the latest projections, the Central Arizona Project and the Arizona Department of Water Resources issued a joint statement. In it, the agencies assure users the state’s top water officials had been anticipating the news.
“The study, while significant, is not a surprise,” the statement reads. “It reflects the impacts of the dry and warm conditions across the Colorado River Basin this year, as well as the effects of a prolonged drought that has impacted the Colorado River water supply.”
Jeff Kightlinger, general manager for the Metropolitan Water District of Southern California, said in a statement the watershed so far has been able to avoid a shortage declaration because of voluntary conservation efforts. But climate change is deepening the Colorado River’s supply and demand imbalance to the point where mandatory cutbacks are coming.